With the progressive development of sciences and technologies, a touch panel is generally integrated on a liquid crystal display screen to form a touch screen, in order for more convenient and effective operations and control. Generally, a touch screen is mainly formed by a display panel, a touch panel and a control circuit.
The display panel widely used at present is a Thin Film Transistor Liquid Crystal Display (TFT-LCD) panel. FIG. 1 is a schematic diagram showing the conventional structure of a display panel. As shown in FIG. 1, the display panel 10 includes a plurality of pixel units arranged in an array. If the display panel 10 is intended for color display, each of the pixel units may include a plurality of sub-pixel units which display different colors, respectively, e.g., three sub-pixel units 11 which respectively display in red, green, and blue (RGB). A Thin Film Transistor (TFT) is used as a driving switch for each pixel unit. Generally, in the display panel 10, the display of each sub-pixel unit 11 is achieved by a display scanning line 13 in the horizontal direction and a data line 12 in the vertical direction. The control circuit includes a gate driving circuit 31 and a source driving circuit 32, where the gate driving circuit 31 generates pulse driving signals respectively for the display scanning lines 13 of the display panel 10 based on a time sequence in order to activate the sub-pixel units 11 corresponding to display scanning line 13 of the above-mentioned line, and then the activated sub-pixel units 11 receive data signals delivered from the source driving circuits 32 through the data lines 12, to display the corresponding gray scales according to the data signals having different voltages.
FIG. 2 is a schematic diagram showing the conventional structure of a touch panel. In combination of FIGS. 1 and 2, a touch panel 20, which is overlapped with the display panel 10, includes a plurality of sensing units 21 arranged in an array. The sensing of each of the sensing units 21 is achieved through a touch scanning line 23 in the horizontal direction and a sensing line 22 in the vertical direction in the display panel 20. The control circuit further includes a touch driving circuit 33 and a sensing driving circuit 34, where the touch driving circuit 33 generates pulse driving signals respectively for the touch scanning lines 23 of the display panel 20 based on a time sequence, and the sensing driving circuit 34 sequentially detects the sensing units 21 connected with the touch scanning line 23 of the above-mentioned line, to determine whether a touch occurs or not, and further to determine the specific location of the touch.
In order for an accurate display effect, the display panel 10 is typically provided with hundreds to thousands of the display scanning lines 13, e.g., 480, 576, or 1024 display scanning lines; while the touch panel 20 is typically provided with more than tens to hundreds of touch scanning lines 23, e.g., 100 touch scanning lines. Therefore, during the scanning process, the scanning time of the display panel 10 is generally greater than that of the touch panel 20.
During the actual touch display process, the control circuit outputs several periodic control signals to enable the scanning of the display panel and the touch panel. FIG. 3 is schematic diagram showing a conventional time sequence allocation in a driving method of a touch screen. As shown in FIG. 3, the frequency (i.e. frame frequency) of the periodic scanning signal is 60 Hz for example, which means that the time duration of each cycle C0 is 16.67 ms, two time sequences, namely a first time sequence C1 and a second time sequence C2, are included in the cycle C0, and preferable time allocation of the cycle C0 is that the time duration of the time sequence C1 is 14.67 ms and the time duration of the time sequence C2 is 2 ms. Within one cycle C0, the control circuit generates and sequentially delivers a plurality of scanning signals to all of the display scanning lines of the display panel during the first time sequence C1 in order to complete one scanning process of the display panel, and then generates and sequentially delivers a plurality of scanning signals to the touch scanning lines of the touch panel during the second time sequence C2 in order to complete one scanning process of the touch panel, and thereafter, the scanning result of the touch panel is processed and analyzed, so as to control the display of the display panel in the next cycle. Therefore, in the conventional scanning mode, the scanning frequency of the touch screen is consistent with that of the display screen.
However, since it is increasingly demanding for the touch sensitivity of the touch panel, the scanning frequency of the touch screen needs to be effectively increased to be above 100 Hz, even above 120 Hz in order to achieve a good touch response speed. However, the scanning frequency of the display panel cannot be increased with that of the touch screen, because the scanning time for each display scanning line of the display panel will be significantly reduced if the scanning frequency of the display panel is excessively high, so that the charge time and discharge time for each sub-pixel unit in the display panel are significantly reduced, which easily causes insufficient charge time and discharge time, thereby degrading the display effect of the display panel. Therefore, it is difficult for the conventional scanning mode to both effectively improve the sensitivity of the touch screen and keep the display effect of the panel display.